Browser: Blocker Card and Settings Card

[cookiengineer]

The Browser Settings Card needs a lookup feature for blockers if the domain matches one of the settings.blockers.

• [x] Create a Blocker Card but with read-only methods, as the private API doesn't allow creating a blocker.
• [x] Integrate Blocker.from() into the Browser Settings Card

[cookiengineer]

As of https://github.com/tholian-network/stealth/commit/f46b6b70ac097f9f524235d5fbdc3059c97b182f this has been implemented and reviewed end-to-end.